Treads of tires are required to have properties including wet-grip performance, fuel economy, and abrasion resistance. Abrasion resistance is important especially for users in the North American market where the average monthly mileage is high. Thus, there is a need to improve abrasion resistance while maintaining wet-grip performance and fuel economy, and even costs.
In general, silica formulations have good wet-grip performance but are inferior in abrasion resistance to carbon black formulations. One possible way to improve abrasion resistance is by increasing the amount of silica or by using fine particle silica having excellent abrasion resistance or a silane coupling agent that strongly binds to polymers. This, however, will increase the cost of the silane coupling agent. Therefore, improving the polymer or the softener is expected to enhance abrasion resistance.
Patent Literature 1 discloses a rubber composition for tire treads whose abrasion resistance, fuel economy, and wet-grip performance are improved by adding a liquid resin having a softening point of −20° C. to 45° C. and a specific silica. This rubber composition still has room for improvement in terms of improving these properties while taking into account costs.